From Wikipedia on 10-Nov-2012
Cooperation (sometimes written co-operation or coöperation) is the process of working or acting together. In its simplest form it involves things working in harmony, while in its more complicated forms, it can involve something as complex as the inner workings of a human being or even the social patterns of a nation. It is the opposite of working separately in competition. Cooperation can also be accomplished by computers, which can handle shared resources simultaneously, while sharing processor time.
Cooperation is the process by which the components of a system work together to achieve the global properties. In other words, individual components that appear to be “selfish” and independent work together to create a highly complex, greater-than-the-sum-of-its-parts system. Examples can be found all around us. The components in a cell work together to keep it living. Neurons create thought and consciousness, other cells work together and communicate to produce multicellular organisms. Organisms form food chains and ecosystems. People form families, tribes, cities and nations. Atoms cooperate in a simple way, by combining to make up molecules. Understanding the mechanisms that create cooperating agents in a system is one of the most important and least well understood phenomena in nature, though there has not been a lack of effort.
Individual action on behalf of a larger system may be coerced (forced), voluntary (freely chosen), or even unintentional, and consequently individuals and groups might act in concert even though they have almost nothing in common as regards interests or goals. Examples of that can be found in market trade, military wars, families, workplaces, schools and prisons, and more generally any institution or organization of which individuals are part (out of own choice, by law, or forced).